how to set up slave amp setup?
 

Can you connect 2 tube bass heads, using one for tone, one for volume, through one cabinet...?

More information needed. What heads? Which one for power, which one for preamping? Pics of front and rear panels might be useful.

you can if the one amp has a pre amp output and the other has a power amp in.

but why 2 heads to run one cabinet? usually 2 amps are used to run more cabinets for volume.

unfortunately tube amps have to have a load on them even if using just the pre. so it defeats the purpose.
both amps would need a speaker load attached.

one heck of a heavy preamp.

It would have to be something like an 810 that has separate inputs for the top 4 10"s and bottom 4 10"s. YOU MUST NEVER CONNECT the outputs of two tube amps together, or SS amps, or a SS with a tube amp.

Once more for better emphasis.

I think what he wants is to get his favourite tone through a bigger amp.

You could with my Mesa amp, it's got a speaker line out that can go into a slave amp to run more cabs, key point being at least two cabs in use or the two half cabs in B-string's example.

I've read there was a Marshall amp or two that were built like that. Tube amp transformers can be paralleled on primaries, secondaries or both, or bridged. SS bridged only, parallel would be bad.

[1], [2]

Never tried it myself.

If they both have tube power sections they both need to have a speaker load before being turned on.

You can indeed do as you suggest but the amps have to be identical and designed with the required operation in mind. Using common bass amps, it's not a good idea.

Tube amps MUST have a speaker cab attached before you turn them on and play anything through them.

You can slave them together to run more cabs, but this is usually done for volume purposes. Each head has to be connected to at least one cab.